1. Technical Field
This invention relates to building construction and to radon control for buildings. Specifically, it relates to a radon gas adsorber for buildings which comprises an open-cell material containing activated carbon and attached to a backing material providing high resistance to radon gas flow. The adsorber prevents flow of radon gas into the building from the ground below it by resisting the gas flow path with the backing material and adsorbing the gas with the activated carbon.
2. Background Art
The threat to health from radon gas in buildings is well known. (See, for example: Radon: The Invisible Threat, M. Lafavore, Rodale Press, 1987, and Radon: A Homeowner's Guide to Detection and Control, B. L. Cohen and D. Nelson, Consumers Union, 1987). Radon in indoor air comes primarily from radium in the soil. Radon is a gas which flows up from the soil into buildings. It is a dangerous vehicle for the dispersion of its shortlived radioactive decay products. Sources of radon infiltration may be very localized, like cracks and seams in basement floors and walls, and drains. However, radon may infiltrate buildings through the pores of concrete foundations and wood floors.
In the building trades, artisans have addressed the radon infiltration problem in several ways. Small fans have been used to provide subfloor ventilation for soil gas dilution and removal before entry into the building (See, for example: JAPCA 39: 305-309 (1989) R. Bocanegra and P. K. Hopke, "Theoretical Evaluation of Indoor Radon Control Using a Carbon Absorption System"). However, the success of this approach is limited to buildings with a low rate of air exchange between the foundation soil and the inside of the building.
Also, exposed earth and sump systems have been covered with impermeable materials, such as sheet metal. And, noticeable cracks and other openings, such as floor-to-wall seams and seams around drains, have been plugged with polymeric sealants. However, the effectiveness of this approach is uncertain, due to the difficulty of identifying and accessing all the infiltration routes.
Also, sub-slab and sub-floor vapor barriers of polyethylene or PVC have been used to block the infiltration path of soil gases. However, these barriers are subject to damage and puncture from rough sub-slab aggregates and from the comings and goings of workmen, reducing their effectiveness.
Also, it is well known that radon may be adsorbed with activated carbon (See, for example, International Geology Review, Vol. 12, No. 7, 873-878 (1967) Y. T. Kapitanov, I. V. Pavlov, N. P. Semikin and A. S. Serdyukova, "Absorption of Radon on Activated Carbon"). And, activated carbon has been included in air filters for adsorbing other gases (See, for example, U.S. Pat. Nos. 4,514,197, 4,793,837, 4,830,643 and U.S. Pat. No. 4,906,263).
However, there is still a need in the building industry for a radon gas adsorber which is durable, effective and safe.